The present invention relates, in general, to integrated circuits and, more specifically, to interconnection of integrated circuits in a parallel, electrical signal bus structure.
Integrated circuits, such as computer and memory chips, are formed on a die that is cut in a thin slice from a semiconductor material crystal. Electrically conductive bonding pads are formed on each die to facilitate the connection of the die to other integrated circuits to form various electronic circuits. Interconnection of numerous dies together into an electronic circuit requires several different levels of electrical conductors. In a first level, bonding wires are mounted on and extend from the bonding pads on the die to larger pads formed on a substrate. Electrically conductive surface traces in the substrate form the second level of conductors and extend from the pads on the substrate connected to the bonding wires to external pins which extend outward from the integrated circuit housing package. The pins form a third level of conductors as they are typically mounted in sockets in a printed circuit board and soldered in place to form a part of an electronic circuit on the printed circuit board.
Many electronic devices, such as computers, are not limited to one printed circuit board, but require multiple boards for large memory capacity, input/output functions, graphic display interfaces, modems, etc. Such multiple printed circuit boards are typically interconnected by some type of backplane wiring. One conventional type of backplane wiring utilizes a large printed circuit board, commonly known as a "motherboard," which has edge card connectors which receive plug-in edge terminals formed on the printed circuit boards containing the integrated circuits and connected to conductive surface tracings on each printed circuit board. Computer data and address lines are arranged in parallel in a "bus" and extend from the integrated circuit dies on each printed circuit board through the backplane wiring to other integrated circuits on other printed circuit boards to form a continuous electrical signal bus extending throughout the entire group of multiple printed circuit boards.
Another type of backplane wiring also utilizes edge card connectors, but, in this arrangement, the edge card connectors on each printed circuit board are interconnected by cable harnesses extending between each printed circuit board.
Regardless of its specific arrangement, the purpose of the backplane wiring is to connect individual integrated circuit dies mounted on printed circuit boards to integrated circuit dies on other printed circuit boards for use in a particular electronic circuit. However, such conventional backplane wiring structures to form electrical signal parallel buses result in a large size and weight for a complete electronic circuit or device. Overall size and weight are major considerations in any electronic device; but are particularly important in military applications as well as commercial applications where small size and weight for easy portability are desirable characteristics.
Thus, it would be desirable to provide an apparatus for interconnecting one integrated circuit die to another in an efficient size and weight manner. It would also be desirable to provide an integrated circuit parallel bus structure which interconnects a plurality of integrated circuit dies in a parallel bus arrangement.